It’s probably as simple as Ecosia pays more than Startpage was willing to. Firefox has been bleeding money and it’s a little frightening to see what was the open source browser struggle to right the ship.

Maybe Mozilla should try harder to also recruit Startpage. More options for users and more money for Mozilla.

It is also noteworthy that Ecosia has been hosted on Amazon and Cloudflare. Any intentional reference due to the trees being planted in the Amazon Rainforest? https://hosting-checker.net/websites/www.ecosia.org

Meanwhile Startpage appears to be hosted at Surfboard Holding BV in the Netherlands. https://hosting-checker.net/websites/www.startpage.com

For privacy you will want to make sure you feel comfortable also putting your trust in these other companies. https://www.ghostery.com/whotracksme/tracking-reach

Amazon: Rank #2

Cloudflare: Rank #3

Surfboard Holding BV: Not in the top 100 trackers listed